Physical verification of PROCESSPLUS® by means of Venturi nozzle cleaning at Forsmark3

Venturi nozzles used for feed water flow measurement are subject to fouling caused by magnetite deposits, depending on the water chemistry prevalent in the specific nuclear power plant, usually building up within 5-8 weeks after cleaning of the nozzle. At this time, the fouling will have come to a saturation point and no more fouling is expected. From this point, the Venturi reading can be used as a reliable feed water flow measurement, if the systematic deviation which is caused by fouling is correctly considered.

In 2011, BTB Jansky installed the online system PROCESSPLUS® at nuclear power plant (NPP) Forsmark 3. The objectives were to assess and monitor feed water mass flow and eventually to correct the Venturi nozzle flow meter. This is done by introducing and applying a reconciled correction factor in order to calculate the reconciled feed water mass flow as input for the reconciled thermal core power.

Up to April 2018, the delta between the thermal core power based on the Venturi nozzle reading and the reconciled thermal core power amounted to approx. 25 MWth, equaling approx. 9 MWe. This value represents the power recovery potential which can be realized after introducing the correction factors determined by PROCESSPLUS®.

One of the projects performed during the 2018 outage at the NPP was the cleaning of the Venturi nozzle. The objectives of the cleaning were:

• To verify the originally indicated power recovery potential/feed water mass flow level by PROCESSPLUS®
• To monitor the fouling process until its saturation point and to determine the new systematic deviation after fouling
• In addition to the already existing mathematical and statistical proof, to serve as the physical proof that PROCESSPLUS® can be used to determine and apply correction factors for feed water flow measurements

As a result, the power recovery potential indicated by PROCESSPLUS® was verified with a realized business case of over SEK 100.000 per day or EUR 3.6 million since realization. Unexpectedly, a re-fouling of the nozzle has either failed to materialize or has been compensated by another, yet unknown effect. Subsequently, the reconciled and measured feed water flow level have stayed at same levels, even a slight downward drift of the feed water flow measurement has been observed. The physical reasons are currently being investigated. For more information go to

Original (Swedish only)

https://group.vattenfall.com/se/nyheter-och-press/nyheter-pressmeddelanden/nyheter/2019/rena-ror-gav-ovantad-effekt

In the Vattenfall magazine "REAKTION" (Pages 18-19)

https://issuu.com/efi4/docs/reaktion__1_2019_issuu